1. Field of the Invention
The present invention relates to a laminated bituminous roofing membrane suitable for use in cold-application type roofing, waterproofing, or dampproofing work in building construction or civil engineering. More specifically, it relates to a laminated bituminous roofing membrane particularly suitable for use in cold application type formation of a single roofing, waterproofing, or dampproofing layer. The term "bituminous" and "bitumen", as used hereinbelow, may be replaced by the term "asphalt".
2. Description of the Prior Art
Heretofore, as is well-known in the art, bituminous roofing membranes or synthetic polymer type roofing sheets have generally been used for roofing, waterproofing, or dampproofing work in building construction or civil engineering.
In one process, in use for a long period of time, two or more layers of bituminous roofing membranes or sheets are laminated at a construction site using hot molten bitumen to form a continuously integrated multilayer roofing or waterproofing layer.
In another process, synthetic polymer type roofing sheets, such as vulcanized rubber sheets, unvulcanized rubber sheets, or synthetic resin sheets, are applied to a substrate while bonding the adjacent sheets to each other at the joint portions thereof to form a substantially single waterproofing layer.
In such waterproofing processes, the waterproofing membranes or sheets themselves must have high durability; the water-tight bonding of the joint portions between adjacent membranes or sheets must be complete; and, if no protective layer such as concrete or gravel is applied over the waterproofing layer, i.e., the waterproofing layer is finished in an exposed state (i.e., exposure-to-the weather type process), no blistering may be caused by vapor pressure of water flowing up through a substrate.
In conventional bituminous waterproofing application processes, although the desired water-tight bonding of the joint portions of the adjacent waterproofing membrane or sheets can be relatively readily effected by using an adhesive composed of a material identical to, or similar to, the bituminous material of the waterproofing membranes or sheets, the conventional bituminous waterproofing membranes or sheets per se have the disadvantage of insufficient durability. To make up for this, a plurality of the bituminous waterproofing membranes or sheets are laminated in, for example, a thickness of about 5 mm to about 10 mm.
This necessitates a large amount of materials and man-hours and, therefore, increases the materials cost and man-power cost required in the waterproofing application processes.
On the other hand, the above-mentioned various kinds of synthetic polymer type waterproofing sheets are generally used in the form of a single layer having a thickness as thin as 1.0 mm to 2.0 mm. Of these sheets, vulcanized rubber sheets are most widely used due to the excellent mechanical strength and weathering properties (or weather resistance) thereof. However, there is the problem of insufficient bonding strength, particularly the durability thereof, of adjacent vulcanized rubber sheets when such sheets are successively applied onto a substrate. Therefore, water leakage often occurs at the joint portions. This is caused by the poor adhesion properties of the sheets due to the vulcanization of the rubber and the absence of appropriate adhesives.